Electromagnetic spectrum is the crude oil of last-mile connectivity, especially in Africa where more traditional kinds of last-mile communication infrastructure are not especially well-developed. As in the oil business, anyone who has gained control of spectrum in the last ten to twenty years has made a great deal of money. But unlike oil, spectrum is something that is much harder to put your finger on. The struggle to understand what kind of thing spectrum is and consequently how it should be managed has led to a lot of disagreement, to the extent that we can’t seem to work out whether it is abundant or running out. In the past couple of years you may have seen articles with titles like these:

Apparently even with our remarkable technical capacity to manufacture smartphones that are more powerful than all of NASA’s computing power in 1969, we still can’t really get to grips with the elusive nature of radio spectrum.  To unpack this problem, let’s go back to basics.

What is Electromagnetic Spectrum and Why Does It Require Regulation?

Spectrum is not actually a thing, it is simply the range of possible frequencies for electromagnetic radiation.  By varying the size and frequency of radio waves, we are capable of sending information wirelessly.  This was first achieved with voice and telegraph but has now evolved into digital communication capable of transmitting anything that can represented digitally from documents to sound to video.

So what does wireless communication look like?  Imagine a still pond into which you have dropped a single pebble. It is easy to see the propagation of waves caused by the stone.  Now imagine twenty people dropping stones into the same pond at the same time.  Can you still see the waves caused by your stone?  Unlikely. This is called interference.  You can no longer see your waves.  While radio waves are not physical waves like water, they interfere with each other in a similar sort of manner.  When the signals from two television stations overlap, you can no longer distinguish the program you wanted to watch.  Counter-intuitively, radio waves are not destroyed when they collide with each other.  They pass through each other.  Thus if you had the magical ability to colour only the waves caused by your pebble, you would clearly see your waves again even though others were dropping pebbles at the same time.  The technical meaning of “interference” is at odds with its more colloquial meaning which is to block or obstruct.  When radio waves interfere they don’t impede each other but they can make the original wave form hard to recognise.

And that brings to the most significant reason why radio spectrum is regulated and that is to prevent interference.  Another reason to regulate spectrum is coordination to encourage people doing similar things and using similar technologies to use the same frequencies. In the early days of wireless communication, interference was an easy problem to solve. The range of available spectrum was vast and demand was comparatively small. Interference could be solved by making sure that people using spectrum in the same geographic region were allocated individual bands of spectrum that were well apart from each other in the spectrum band.  This strategy was reasonably successful for nearly 70 years.

And so things might have continued to this day had it not been for the explosion of demand for wireless spectrum from broadband service providers and mobile operators. In the last 15 years, spectrum has gone from an abundant to an apparently scarce resource. But is it truly scarce? It is certainly true that demand currently exceeds supply but there is debate as to the nature of the scarcity and that debate is rooted in the nature of what spectrum is and how, as a result, it should be treated.

So What Kind of a Thing is Spectrum?

A key consideration when looking at public versus private access to any resource is whether that resource is rival or not i.e. does use of it by one person preclude use by another. Rival goods tend to become private property whereas non-rival goods such as solar power, for example, are public goods that do not require explicit management. And of course there is a range of goods in between which are partially rival such as the oceans and nature in general which are non-rival as long as care is taken to ensure the resource is tended and non-overused. Historically, regulators have been obliged to treat spectrum as a rival good because of interference. In fact, in order to ensure the absence of interference for television broadcasters, regulators were obliged to establish spectrum frequency no-man’s-lands between television channels to reduce the chances of stray interference.  However, the now rapid evolution of both wireless and information technology obliges us to reconsider how we think about spectrum and spectrum management.  Is spectrum a rival resource?  The answer is fuzzier than it used to be.

Technological increases in efficiency

First we have to acknowledge the steady increase in spectral efficiency in wireless technologies. Every year we are able to pack more data into less spectrum with less power. This efficiency is typically expressed as bits per hertz per km2.  While spectrum is not infinite, the trend towards efficiency increase shows no immediate sign of slowing down. In fact, wireless pioneer Martin Cooper has coined a law similar to Moore’s Law in which he argues that spectral efficiency has doubled every 30 months since Marconi patented the wireless telegraph in 1897.  The evolution of radio and antenna design has meant that with increased sensitivity we can now communicate the same information with much less power.  You can imagine old television broadcast transmitters as effectively having to “shout” at the relatively deaf television sets.  But sensitivity is only part of the story.  Engineers are making great strides in mitigating wireless interference. It is increasingly possible to design wireless technologies which are sensitive to other radio transmissions and which can operate in “noisy” environments.  The scenario described above where one might be able to recognise the pond waves from ones own pebble is now increasingly possible through techniques like beamforming with multiple antennas.

Administrative increases in efficiency 

Imagine having a hotel room permanently reserved for you in every city in your country.  No matter where or when you travel, you room is always ready.  Great for you but a bit of tough business for the hotel owner.  This is effectively how early spectrum regulation operated and it was feasible because capacity far exceeded demand.  With the situation now reversed, regulators have had to embrace a more nuanced approach to the different dimensions of spectrum.  Here are some of the different ways in which spectrum can be administered:

More control of radio propagation means that we regulate different for different regions in a country.  This might mean having different spectrum license holders in different areas or it might mean varying the allowable power output based on geography.

The proximity of devices to each other can make a difference.  Low power devices that are nearby each other can operate in the same spectrum as much higher power technology but below its “noise floor“.  Imagine two people talking to each other at a rock concert.  Their conversation doesn’t interfere with a the very loud concert yet they are close enough to communicate with each other “at low power”.  I am grateful to Sascha Meinrath for that extremely apt analogy.  

Some spectrum technologies have a specific orientation, that is to say as opposed to radiating generally, they are pointed in a specific direction.  Satellites are a great example of this.  They obvious point upwards.  This creates an opportunity for re-use of the spectrum in ways that don’t point up e.g. point-to-point terrestrial links.  Another means of reducing interference is to use antenna designs that polarise communication i.e. radio waves propagate orthogonally to each other and so reduce interference.

Spectrum can also be shared in time.  This could happen in big chunks such as someone using television spectrum late at night when the station is not broadcasting to sharing of micro slices of time.  Thanks to computing technology, it is possible for the same spectrum to be automatically shared in tiny time slices which give the appearance of continuous connectivity.

Letting Technology Handle the Administration

To date the regulation of spectrum has largely relied on human management and oversight.  This places a significant burden on the regulator and is necessarily somewhat slow.  New technologies offer the potential for the use of spectrum to be managed dynamically via a database.  This would not only lower the barrier to access but could be used to ensure fair play among spectrum holders.  Allowing computer systems to dynamically assign spectrum on demand could create both spectrum and organisational efficiencies. 

Not All Spectrum Is Created Equal

A final important thing to know about spectrum is that not all wireless spectrum is created equal. At the lower frequency end of the radio spectrum, radio waves tend to have better propagation characteristics than at higher frequencies. This means they have better reach because they are capable of travelling through solid objects with less signal loss. Thus radio spectrum at the lower frequencies are often considered quite valuable because fewer transmitters are required to cover an equivalent area at a higher frequency. There is a trade-off though: the physics of lower frequencies present bigger constraints to broadband capacity than higher frequencies.  So higher frequencies can carry more data but don’t propagate as well while lower frequencies have much better range but are more limited in terms of throughput.

So Is There a Crisis?

Perhaps crisis is the wrong word.  Are we running out of spectrum?  The answer to that seems to clearly be that ongoing innovation and efficiency increases will ensure we don’t run out of spectrum for some time to come.  So no crisis?  Well, not exactly.  We still haven’t worked out a very satisfying means of deciding who gets what spectrum and for how long.  As a result, there is an apparent scarcity of spectrum as debate about how best to make spectrum available leads to delays, confusion, and missed opportunities.  More about that in the next posts in this series.

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Water images courtesy of Snappy.joneS 2006 BY-NC-SA and Marc Dezemery 2006 BY-NC-ND

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Google and Microsoft

After a welcome by Minister Cheikh Abiboulaye Dieye, I moderated the first session giving first a brief introduction to TVWS.  Much more interesting though were the two key presenters for the first session:  Kai Wulff  of Google and Paul Mitchell of Microsoft. To have Google and Microsoft on the same stage making common cause for affordable access through TV White Spaces spectrum is a bit of a dream come true for me.  For Microsoft and Google this is very much a case of the enemy of my enemy is my friend.  They compete in search, mapping, mobiles and just about everything else but in this case Google and Microsoft share an enemy in the high cost of access in Africa.  Both stand to benefit from having more Africans affordably online and in this particular case, their corporate goals are fairly well-aligned with a development goal.  And on that front, standby for news in June of a new industry association on dynamic spectrum supported by both Google and Microsoft.

What stuck in my mind from this session was an interesting analogy shared by Kai Wulff who pointed out that in Africa, taxi drivers generally don’t fill up their tank completely but just enough to get where they need to go.  Similarly, pay-as-you-go airtime has allows for dynamic management of phone charges.  This is common knowledge but it was a nice insight that this conceptual framework might be applied to spectrum management.

Pilots and Trials

So what’s going on in Africa with TVWS?  A lot.  Both Google and Microsoft are sponsors of significant of trials in Africa; Google in South Africa and Microsoft in Kenya.  There are also independent efforts going on in Malawi.  Here’s an update on them.

South Africa

The Google-sponsored trial in the Western Cape of South Africa is a small success story in collaboration.  TVWS technology was initially instigated by an active civil society and by the Wireless Access Providers Association (WAPA).  After gaining the attention and then support of Google, other key players came on board.

• TENET, the South African National Research and Education Network (NREN), offered to be the project manager for a TVWS trial;
• ICASA, the South African communications regulator,  expressed its support for the trial;
• CSIR, the Council for Scientific and Industrial Research, a parastatal research agency, offered to carry out the necessary spectrum measurements to provide the necessary evidence of non-interference that would pave the way towards regulation; and,
• the e-Schools Network provided a local network of schools in need of affordable access to be connected through the trial.

Arno Hart, TENET’s project manager for the trial, presented the work of the trial so far.  So far 10 schools have been connected representing more than 6400 students.  So far the technology has met its most important goal which is demonstrating non-interference with television broadcasts.  Cape Town has more active terrestrial television broadcast channels than most place in South Africa so it was ideal for a trial of TVWS.  The throughput and latency of the connectivity is not quite the 10mbps over 8km that has been advertised but it was still respectable.  It is evident that TVWS technology is still evolving and performance improvements can be expected.

Arno’s talk had lots of interesting insights into TVWS such as the fact that the frequencies below an in-use television channel are more sensitive to interference in the frequency directly above the channel.  This is because the lower end of the television channel is a marker that helps define the wave form for the channel.  Interfering with this marker has a bigger impact on the television broadcast than interference at the top end of the channel.  Critical information like this will help shape the spectrum authentication database that will determine what television spectrum can be used for TVWS access and where.  You can read more about the trial on TENET’s website.

Kenya

The genesis of the TVWS pilot in Kenya is a little different.  It was inspired by one of the true pioneers of connectivity in Africa, Malcolm Brew.  Years ago Malcolm was the CTO of Bushnet Uganda, a company building HF radio links into rural Uganda and the DRC to deliver email into areas previously considered inaccessible except by satellite.  Having since moved back to the Isle of Bute in his native Scotland, Malcolm convinced British Telecom to run a TV White Spaces trial on the Isle.  Paul Henderson, chair of Indigo Telecom, a Kenya satellite services provider, happened to call Malcolm and was amazed by the quality of their Skype call over the TVWS connection.  He immediately saw the potential of TVWS for rural Kenya and, with the support of Microsoft and USAID, has rolled out a pilot in Nanyuki, Kenya.  You can read more about the pilot on Microsoft’s website.

While this pilot has gone ahead with a lot of international support, its internal support is a little more complex.  The pilot enjoys support from the Ministry of Information and Communications but it doesn’t appear that the communication regulator (CCK) are particularly involved in the trial.   I was disappointed not to see someone from CCK at the Dakar event.  Moving forward it will be essential to engage more closely with the regulator as they are crucial to the success of TVWS.

Malawi

Another very interesting trial is getting underway in Malawi.  Championed by Dr. Chomora Mikeka of the University of Malawi and Jonathan Pinifolo of the Malawi communications regulator (MACRA), they are carrying out background research in anticipation of setting up a pilot in a few months.  They have partnered with the International Centre for Theoretical Physics (ICTP) in Trieste who have a long history of supporting wireless research in African universities.

What I found interesting about their story so far was their innovative approach.  Among other things, they have developed a very low-cost spectrum analyser based on Open Hardware which has allowed them to carry out a spectrum survey at a fraction of the typical cost.  In listening to Dr. Mikeka, it was evident to me that Africa has the potential not just to be a leader in regulatory innovation around TVWS but a technology leader as well.

Others

And of course there is more going on.  Microsoft is supporting other pilots in Tanzania and soon in the Limpopo province in South Africa.  In Nigeria, a company called WaveTek has secured the West African distribution rights for Carlson Wireless and is on the verge of carrying out a trial.

Manufacturers and Wireless Standards

There are an array of competing standards around TVWS technology.  First there is the 802.22 standard also known as Wi-Far which has evolved out of the WiMax standards group.  Next there is the 802.11af standard also known as White-Fi which has evolved out of the WiFi standards group.  Then there is also the Weightless standard which has been put forward by Neul, one of the earliest developers of TVWS technology.  Neul developed its own Weightless standard because they originally designed their TVWS technology for machine to machine (M2M) communication.  As the demand for TVWS in rural broadband applications became more apparent, they adapted their Weightless standard for broadband use.  Finally there is the wild card in the mix, the TD-LTE standard for White Spaces being developed by Huawei.

Neul have licensed their technology to Carlson Wireless so currently all Carlson equipment also uses the Weightless standard.  Interesting to note that Neul are also releasing their own equipment shortly which will perhaps end up competing with Carlson.  The South African TVWS trial is using Carlson equipment as is the Malawi trial.  In Kenya, the TVWS pilot is being carried out with Adaptrum equipment.  Adaptrum currently use the 802.22 standard or something fairly close to that standard.

So which standard is likely to dominate?  That was what I hoped to find out more about at the event but I was disappointed.  Manufacturers were pretty vague on the topic.  When I asked the question, I didn’t get much more than “the market will decide”.  On the one hand letting the market decide is a good thing but on the other hand, the balkanisation of the standards community makes it hard to build momentum.

From what I can make out so far, 802.22 is designed for rural broadband but is not that well-loved by manufacturers because it is a complex standard to implement.  802.11af is simpler and easier to get to market but suffers some of the limitations of its WiFi parentage.  Weightless appears to have an early advantage but will other manufacturers really but into a standard so closely associated with one company?  Finally, TD-LTE doesn’t currently feature in any trials and is targeted at the mobile industry not the rural broadband industry but it would be a mistake to discount Huawei from any calculations in this arena.  I found it a bit hard to understand the presenter from Huawei but I believe a typical use case for TD-LTE White Spaces would be something like backhaul and coordination among femtocells.  While an interesting and possibly very efficient use of TVWS, the TD-LTE approach holds much less interest for me because it puts TVWS directly into the mobile operator supply chain as opposed to enabling entrepreneurship that could lead to more competition in the broadband marketplace.

White Spaces and the Authentication Database

Although it didn’t start out that way, TVWS technology is now inextricably connected with the concept of an authentication database.  Early proponents of TVWS argued for a spectrum-sensing approach to regulation where TVWS devices would regularly “sniff” the spectrum to see if it was in-use by the primary spectrum holder and dynamically switch out of any occupied spectrum. There was sufficient push-back from broadcasters on viability of spectrum sensing that an alternative had to be devised.  This alternative came in form of an authentication database that all TVWS devices are obliged to connect to in order to receive information about available spectrum in their area.

Andy Lee of Google gave a great presentation explaining the basics of how the authentication database works.  In short, the database combines information about spectrum in use with information about the geography of the region and performs a calculation to determine where current broadcasts reach and on what frequencies.  It then uses the inverse of that to establish what spectrum is free for use and where.

In Africa, even in urban areas, it is clear that there is a lot of unused television spectrum that could be re-purposed for TVWS rural broadband applications.

A lot of work has been done in the US and elsewhere to establish an open standard for TVWS databases. The Internet Engineering Task Force have developed the PAWS standard for accessing TVWS databases.  While different companies have developed TVWS database applications, Google and Telcordia among them, they all operate according to a common standard.  Thus it is possible to have more than one authentication database in a country.

In terms of regulation and TVWS databases, it is worth noting that there is one significant difference between US and UK regulation of TVWS.  In the UK, the power output of the TVWS device is not pre-determined but can be dynamically set via the database.  Thus if the database knows that the device is in a remote areas with few or no terrestrial television broadcasters, it can permit the TVWS to operate at a higher power output offering better range and throughput.

There was some discussion among the participants as to whether an authentication database was the best approach to TVWS for Africa.  Some people argued that this was importing unnecessary limitations from the US.  It is an interesting question.  On the one hand, I would like to see TVWS achieve the same kind of success that WiFi has through an unlicensed environment.  I fear that constraints such as an authentication database might limit the uptake of the technology.  On the other hand, variable power output (described above) which a database enables is a significant advantage.  In addition, an authentication database also offers a big security blanket to regulators who need not worry that they are opening Pandora’s Box because they ultimately are still in complete control of the spectrum.  This may prove to be a critical ingredient to speed adoption.

The Regulators

Most interesting of all was what the African communication regulators had to say.   Speaking at the event were representatives from the communication regulators in Senegal, Niger, Malawi, and South Africa.  In the audience, there was representation from communication regulators of Benin, Cameroon, Cape Verde, Ivory Coast, Nigeria, and Togo.  What was most striking for me was the wide range of perspectives on TVWS. Some regulators clearly saw the potential and were working to integrate TVWS into their strategic planning and others were frankly sceptical.  Of those who were doubtful of TVWS technology, a lot of the concern centred around the fact that television spectrum was already a subject of heated debate related to the Digital Switchover and the potential release of one or more IMT bands for mobile use.  The spectrum bands in question,  700MHz and 800MHz,  form the upper block of the UHF television band.  I have my own opinions about how this could be handled but it is clear that there is a lot of interest in television spectrum and, as a result, a lot of concern that it be handled appropriately.   It was proposed by some that TVWS should wait until the Digital Switchover was complete and firm agreements had been made on new IMT bands such as the 700MHz band.  In my opinion, making these issues dependent on each other robs TVWS technology of its primary innovation, the ability to continuously and dynamically adapt to a changing spectrum regulatory landscape.  One thing is clear to me and that is that more awareness raising and healthy debate of TVWS needed.

No discussion of regulators would be complete without mentioning the stand-out presentation from the UK regulator (OFCOM)’s head of spectrum, Prof H Nwana.  Prof Nwana’s roots are in Cameroon but at OFCOM he leads what is arguably the most progressive approach to dynamic spectrum regulation in the world.  His vision of the evolution of dynamic spectrum management is inspiring.

Summary

This is a watershed moment for Television White Spaces in Africa.  There is a lot going on.  With the backing of companies like Microsoft and Google, TVWS are getting recognition as a key part of the regulatory toolbox.  Manufacturing is starting to come on board but the process is a little slower than anyone had hoped.  TVWS equipment has yet to achieve its full mass market potential.  Equally the standards for TVWS are still evolving.  Expect to see one of these standards leap forwards in the next 24 months.  The tide of TVWS is at the flood and it is up to African governments, regulators, and entrepreneurs to decide whether to seize it or not.

All the presentations from the TV White Spaces Africa Forum 2013 are available online. Kudos to Google and all the other partners for making this extremely worthwhile event happen.  Finally, if I have missed nuances or missed the mark entirely on any of the above, please do correct me.

However things turn out, it is clear to me that we need a better understanding of the choices and their implications.  While most of my time is still taken up with Village Telco, I am very happy to say that I am now also affiliated with the Network Startup Resource Centre (NSRC), an organisation that has dedicated itself to building the capacity of Internet network operators around the globe . My role with them is to build understanding of the opportunity that shared spectrum technologies and policies represent.

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One of the early mistakes we made with the Mesh Potato was not placing sufficient emphasis early on, on getting type approval for the Mesh Potato and indeed focusing on both European and U.S. type approval.  What is type approval you ask?  Type approval is the magic glue that makes unlicensed spectrum work.  Many people take the term unlicensed to mean unregulated but nothing could be further from the the truth.  Unlicensed spectrum succeeds because the devices that are permitted to use unlicensed spectrum are carefully regulated to ensure that they conform to strict standards in terms of power output and many other technical specifications that ensure that unlicensed devices “play nicely” with each other.

I am happy to say that this issued has finally been addressed in full and Mesh Potatoes now enjoy full compliance with both the standards of the Federal Communications Commission (FCC) of the United States and the European Union’s CE standard.  These are the two most common international standards for compliance and should ensure that the Mesh Potato can conform to almost any regulatory regime.

If you would like to get copies of the certification in order to apply for local type approval in your country, please get in contact with us via this website.

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